Adding Textarea to Edit Category does not store the input

Hi There,

I tried to add a second textarea to categories by using this guide. But that entry will not be saved and I do not know which command print that text on the website. Does anyone have an idea?

Code in my functions.php:

add_action('course_edit_form_fields','course_edit_form_fields');
	  add_action('course_edit_form', 'course_edit_form');
	  add_action('course_add_form_fields','course_edit_form_fields');
	  add_action('course_add_form','course_edit_form');

	  function course_edit_form() {
	  ?>
	  <script type="text/javascript">
	  jQuery(document).ready(function(){
	  jQuery('#edittag').attr( "enctype", "multipart/form-data" ).attr( "encoding", "multipart/form-data" );
			  });
	  </script>
	  <?php
	  }

	  function course_edit_form_fields () {
	  ?>
    <tr class="form-field">
            <th valign="top" scope="row">
                <label for="catpic"><?php _e('Addtional Description', ''); ?></label>
            </th>
            <td>
				<textarea name="description_bottom" id="description_bottom" rows="5" cols="50" class="large-text"></textarea><br />
                <span class="description">Second Description</span>
            </td>
        </tr>
        <?php
    }

I also searching for a plugin to do this, but there is not one that can produce such a extra field.

So how can I save that input and how can i get it?
Thank you.